A synthesis of γ-trifluoromethyl α,β-unsaturated γ-butyrolactones using CF3SiMe3 as a trifluoromethylating agent

A general synthesis of γ-trifluoromethyl α,β-unsaturated γ-butyrolactones is described. The fluoride-catalyzed nucleophilic addition of a trifluoromethyl (CF3) group generated from (trifluoromethyl)trimethylsilane (CF3SiMe3, Ruppert–Prakash reagent) to a masked maleic anhydride 1 (cyclopentadiene–maleic anhydride adduct) provides the corresponding adducts 2 with high stereoselectivity. The γ-trifluoromethyl α,β-unsaturated γ-butyrolactones 4 were obtained after treatment of the adducts 2 with Grignard reagents, followed by flash-vacuum pyrolysis.